avfilter/avfilter: add sample_count_in and sample_count_out

libavfilter/avfilter.c

@@ -1013,6 +1013,7 @@ int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
 
     link->frame_blocked_in = link->frame_wanted_out = 0;
     link->frame_count_in++;
+    link->sample_count_in += frame->nb_samples;
     filter_unblock(link->dst);
     ret = ff_framequeue_add(&link->fifo, frame);
     if (ret < 0) {
@@ -1372,6 +1373,7 @@ static void consume_update(AVFilterLink *link, const AVFrame *frame)
     ff_inlink_process_commands(link, frame);
     link->dst->is_disabled = !ff_inlink_evaluate_timeline_at_frame(link, frame);
     link->frame_count_out++;
+    link->sample_count_out += frame->nb_samples;
 }
 
 int ff_inlink_consume_frame(AVFilterLink *link, AVFrame **rframe)

libavfilter/avfilter.h

@@ -584,6 +584,11 @@ struct AVFilterLink {
      */
     int64_t frame_count_in, frame_count_out;
 
+    /**
+     * Number of past samples sent through the link.
+     */
+    int64_t sample_count_in, sample_count_out;
+
     /**
      * A pointer to a FFFramePool struct.
      */